Parasitism Tapeworms live in the intestines of mammals, where they absorb large amounts of their hosts' food. Fleas, ticks, lice, and leeches live on the bodies of mammals, feeding on their blood and skin, as seen in Figure 4–10. These are examples of parasitism (PAR uh sit iz um), relationships in which one organism lives inside or on another organism and harms it. The parasite obtains all or part of its nutritional needs from the host organism. Generally, parasites weaken but do not kill their host, which is usually larger than the parasite.
Commensalism Small marine animals called barnacles often attach themselves to a whale's skin, as seen in Figure 4–11. The barnacles perform no known service to the whale, nor do they harm it. Yet the barnacles benefit from the constant movement of water—that is full of food particles—past the swimming whale. This is an example of commensalism (kuh MEN sul iz um), a relationship in which one organism benefits and the other is neither helped nor harmed.
FIGURE 4–10 Parasitism This brown leech is feeding on the blood of its host, a human. In a parasitic relationship, the parasite benefits while the host is harmed.
FIGURE 4–11 Commensalism The barnacles attached to the skin of this grey whale are feeding on food in the water that passes over them as the whale swims. Although the barnacles clearly benefit from their relationship with the whale, they do not appear to affect the whale positively or negatively.
4.2 Assessment
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Review What is the difference between a habitat and a niche?
Use Analogies How is a niche like a profession? In ecological terms, describe your niche.
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Review What is competition? Why can't two organisms compete if they live in different habitats?
Interpret Visuals Look at Figure 4–7 and describe how the three species of warblers have divided their resources. Does each warbler have its own niche?
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Review What is a keystone species?
Infer How might a dramatic decrease in vegetation lead to a decrease in a prey species? (Hint: Think of how the vegetation, prey, and predator coold be connected in a food chain.)
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Review What is symbiosis? What are the three major types of symbiosis?
Explain Bacteria living in a cow's stomach help the cow break down the cellulose in grass, gaining nutrients in the process. Is this an example of commensalism or mutualism? Explain your answer.
c. Apply Concepts What is the difference between a predator and a parasite? Explain your answer.
BUILD VOCABULARY
The suffix -ism means “the act, practice, or result of.” Look up the meaning of mutual, and write a definition for mutualism.
Table of Contents
- Formulas and Equations
- Applying Formulas and Equations
- Mean, Median, and Mode
- Estimation
- Using Measurements in Calculations
- Effects of Measurement Errors
- Accuracy
- Precision
- Comparing Accuracy and Precision
- Significant Figures
- Calculating With Significant Figures
- Scientific Notation
- Calculating With Scientific Notation
- Dimensional Analysis
- Applying Dimensional Analysis